Ratna Dewi Kusumaningtyasa,b, Arief Budimana, Sutijana,

Suryo Purwonoa, Dyah Retno Sawitria

a Chemical Engineering Department, Gadjah Mada University, Indonesiab Faculty of Engineering, Semarang State University , Indonesia

DESIGN OF REACTIVE DISTILLATION PROCESS

FOR A SUSTAINABLE BIODIESEL PRODUCTION

FROM PALM OIL

INTRODUCTION

Renewable Energy Resources:

feasible, environmentally friendly,

sustainable

Diminishing of Fossil- Based Fuel

Biodiesel

INTRODUCTION

Common Biodiesel Production Process:

alkaline-catalyzed transesterification of vegetable oils with

short chain alcohols in batch reactor

Transesterification: consecutive, reversible reactions

Batch Reactor:

Labor intensive, low in productivity

Continuous Process:

preferred for large-scale production

Continuous Reactive Distillation

developed for biodiesel production

Main parameters: reflux ratio, feed plate,

distillate rate, number of plates

INTRODUCTION

Reactive Distillation: integrating a simultaneous function of

reaction and separation in a single unit (Budiman et al., 2006)

Shift the equilibrium to the right Reaction completion

Heat Integration Energy efficiency

Reduced number of equipments Lower capital cost

INTRODUCTION

Mathematical Model of Reactive Distillation (RD):

Model on the Separation Zone

Equilibrium model (EQ)

- MESH (Material balance, vapor-liquid Equilibria, mole fraction

Summations, Heat balance).

- Efficiency factor

- Broadly applied

Non equilibrium model (NEQ) - Rate Based Model

- No consideration of the efficiency factor

- Requires empirical data, semi empirical parameters,

and complex equations.

MODELING of RD

MODELING of RD

Model on the Separation Zone

MODELING of RD

Model on the Reactive Zone

As reaction occurs on the liquid phase, equations of overall

mass balance and mass balance of the components should be

corrected, the other equations are yet applicable

A simulation applying EQ model is performed utilizing

ASPEN Plus Version 11.1

The model is an improvement upon the previous work,

in which the reaction presumably occured along the

column (Sutijan et al., 2008).

This model: Assumes that the column consists of 3

zones (rectifying, raction, and stripping zones).

Rectifying and stripping zones are above and below

the reaction zone, respectively (Sneesby,1998).

SIMULATION

Case Study:

Reactive Distillation for transesterification of palm oil.

Flowrate of methanol & palm oil : 300 &100 mole/hr

Number of stage (N) : 10

(excl. Condensor and reboiler)

Reflux ratio (R) : 2

Distillate rate (D) : 100 kmol/ hr

Feed Stage (Nf) : 5

The reaction zone : N=4 to N=7.

The avg. residence time : 10 minutes.

The conversion achieved is 81.57%.

RESULT & DISCUSSION

Sensitivity Analysis :

Having run the initial simulation, sensitivity

analysis is conducted to evaluate the

effect of main parameters on the

conversion.

Sensitivity is the tool provided by ASPEN

for analyzing behavior of the process

and estimate the value trend of a

certain variable

RESULT & DISCUSSION

Effects of Reflux Ratio

The increase on reflux ratio results in the slightly increasing on the

conversion. R=1 XA = 80.25% ; R=10 XA= 88.25%

The higher reflux ratio, the higher condensor and reboiler duty

R=1 Qc = 1952.87 kJ/sec QB = 13763.11 kJ/sec

R= 10.0 Qc = 10740.82 kJ/sec QB = 22971.09 kJ/sec

RESULT & DISCUSSION

78.00

80.00

82.00

84.00

86.00

88.00

90.00

92.00

94.00

0 5 10 15 20

Co

nv

ers

ion

, %

Reflux ratio

0

5000

10000

15000

20000

25000

30000

35000

0 5 10 15 20

Q, kJ/s

ec

Reflux ratio

Reboiler Condenser

Effects of Reflux Ratio

The conversion increase is due to the increase on the

reflux ratio, complemented by the addition of

methanol (methanol recovery) from the column top.

The methanol recovery leads to the higher ratio of

methanol to palm oil excess methanol

shifts the reaction to the right higher conversion.

RESULT & DISCUSSION

Effects of Feed Plate location

Shifting the feed point location:

Nf = 2 to 6 relatively constant conversion

Nf = 7 to 9 the conversion decreases

Once the input of the feed is set too lower in the column,

the reaction time will get shorter.

RESULT & DISCUSSION

0

10

20

30

40

50

60

70

80

90

2 3 4 5 6 7 8 9

Co

nvers

ion

, %

Feed stage

Effects of Distillate Flow

Increasing of the distillate flow (D= 60 to 260 mole/hr) brings

about the decrease on the conversion

(XA= 87.27% to 26.48%)

The low flow of the distillate indicates the high methanol

recovery, causing the excess methanol on the reactive zone.

RESULT & DISCUSSION

0

10

20

30

40

50

60

70

80

90

100

40 60 80 100 120 140 160 180 200 220 240 260 280 300

Co

nvers

ion

, %

Distillate Rate, KMole/ Hr

Effects of Number of the Plates

For D= 60 mole/hr:

The raising on the plates number (N= 4 to 10) provides

enhancement on the conversion (XA= 67.17 to 81.57%).

The increase on the plates number in the column gives

a longer residence time, resulting in the higher conversion

of palm oil to biodiesel

RESULT & DISCUSSION

0

10

20

30

40

50

60

70

80

90

2 3 4 5 6 7 8 9 10 11 12

Co

nvers

ion

, %

Stage Number

RESULT & DISCUSSION

A simulation for biodiesel production from palm oil

taking into account an EQ model with 3 main zones

of the RD column using ASPEN Plus 11.1

results in the best conversion of 87.27% at:

N=10, R= 2, D= 60 kmole/hr, and Nf= 5.

It is higher than that achieved by the previous work,

which gives conversion of 86.91%

(Sutijan et al., 2008).

CONCLUSION

The increase on the reflux ratio the increasing on the

conversion, the condensor (Qc) and reboiler duty (QB).

Shifting the feed point location:

Nf = 2 to 6 relatively constant conversion

Nf = 7 to 9 the conversion decreases

The higher distillate flow the lower conversion achieved

The raising on the number of the plates from N= 4 to 10

provides significant enhancement on the conversion.

The best conversion is 87.27%, achieved at :

N=10, R= 2, D= 60 kmole/hr, and Nf= 5.

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